[infra] Remove last remnants of old checked in SDK

* Update README.
* Create 32-bit Windows CIPD package in update.sh.
* Remove architecture specific executable names.

Change-Id: I553b282188bc76e82df0a6e40200e3311fdc6f1d
Reviewed-on: https://dart-review.googlesource.com/62842
Commit-Queue: Alexander Thomas <athom@google.com>
Reviewed-by: Zach Anderson <zra@google.com>

tools/sdks/README

@@ -1,19 +1,13 @@
-This directory contains the hashes of tar.gz files uploaded to cloud storage.
-Hooks in the DEPS files run "download_from_google_storage" to download these
-tarfiles, and unpack them. These tar files contain a stable Dart SDK, which
-is used to build the observatory and to run the test scripts.
+This directory contains a stable Dart SDK, which is used to build the
+observatory and to run the test scripts.
 
-The hooks use the --auto-platform feature, so that only the SDK for the
-current platform (linux, macos, or windows) is downloaded. This requires
-the subdirectories to have the special names "linux", "win", and "mac", which
-the download script is hardcoded to recognize.
+The DEPS use CIPD's ${platform} syntax find the right SDK for the platform.
 
-The linux SDK has two extra dart executables added to the bin directory.
-'dart-arm' and 'dart-arm64' are executables compiled to run on
-arm and arm64 (aarch64) processors, respectively. We are currently
-using the 32-bit ia32 build as the default on windows, and the 64-bit x64
-build as the default on linux and macos.
+We are currently using the 32-bit ia32 build as the default on Windows, and the
+64-bit x64 build as the default on Linux and Mac. arm and arm64 CIPD packages
+are used on Linux.
 
-To upload new versions of these tar files, run "./update.sh" in this directory.
-Because these SDKs are used for the presubmit dartfmt check on changed files,
-they may need to be updated often when dartfmt is changing rapidly.
+To upload new versions of these CIPD packages, run "./update.sh" in this
+directory. Because these SDKs are used for the presubmit dartfmt check on
+changed files, they may need to be updated often when dartfmt is changing
+rapidly. Access to the project-dart-admins Luci auth group is required to do so.

tools/sdks/update.sh

@@ -60,6 +60,7 @@ cipd create \
   -ref $channel
 rm -rf sdk
 
+# We currently use the ia32 SDK on x64 Windows as well, see also README.
 gsutil cp "gs://dart-archive/channels/$channel/release/$1/sdk/dartsdk-windows-ia32-release.zip" .
 unzip -q dartsdk-windows-ia32-release.zip -d sdk
 cipd create \
@@ -70,4 +71,14 @@ cipd create \
   -ref $channel
 rm -rf sdk
 
+gsutil cp "gs://dart-archive/channels/$channel/release/$1/sdk/dartsdk-windows-ia32-release.zip" .
+unzip -q dartsdk-windows-ia32-release.zip -d sdk
+cipd create \
+  -name dart/dart-sdk/windows-386 \
+  -in sdk \
+  -install-mode copy \
+  -tag version:$1 \
+  -ref $channel
+rm -rf sdk
+
 popd

tools/utils.py

@@ -683,22 +683,8 @@ def CheckedInSdkExecutable():
   name = 'dart'
   if IsWindows():
     name = 'dart.exe'
-  elif GuessOS() == 'linux':
-    arch = GuessArchitecture()
-    if arch == 'arm':
-      name = 'dart-arm'
-    elif arch == 'arm64':
-      name = 'dart-arm64'
-    elif arch == 'armv5te':
-      # TODO(zra): This binary does not exist, yet. Check one in once we have
-      # sufficient stability.
-      name = 'dart-armv5te'
-    elif arch == 'armv6':
-      # TODO(zra): Ditto.
-      name = 'dart-armv6'
   return os.path.join(CheckedInSdkPath(), 'bin', name)
 
-
 def CheckedInSdkCheckExecutable():
   executable = CheckedInSdkExecutable()
   canary_script = os.path.join(os.path.dirname(os.path.realpath(__file__)),